Thread-cutting mechanism for sewing machines



A. F. FIFIELD. THREAD cumms MECHANISM FOR SEWING MACHINES.

2 SHEETS-SHEET 1.

FILED DEC. 1, 19:1.

INVENTO wffm ATTORNEY Jan, 16, 1923.

A.'F. FIFIELDr I THREAD CUTTING MECHANISM FOR SEWING MACHINES.

ZVSHEETS-LISYHEET 2.

FILED DEC. 1, 1917 ATTORN E Patented Jan. 16, 1923.

UNITED 'STATES PATENT OFFICE.

ALBERT F. EIEI LD, 0E E ARK, NEW JERSEY, ASSIGNOR TO THE SINGER MANUEAc- TUBING COMPANY, A CORPORATION or NEW JERSEY.

THREAD-CUTTING -MECHA1\TISM FOR SEWING MACHINES.

Application filed Decemberl, 1917. Serial No. 204,870. 7

To all whom it may concern:

Be it known that I, ALBERT F. FIFIELD, a citizen of the United States, residing at Newark, in the county of Essex and State of New Jersey, have invented certain new and useful Improvements in T hread-Cutting Mechanism for Sewing Machines, of which the following is a specification, reference being had therein to the accompanying drawings.

This invention relates to thread cutting mechanism for sewing machines of the type commonly used for sewing on buttons, tacking and barring operations or the like wherein it is desired to form detached series or roups of fastening stitches.

f the various thread-cutting mechanisms now known and used, some are too complicated and costly to manufacture. Others employ knives which are so mounted and operated that they will not cut the thread clean unless they are frequently sharpened. Still others will not trim ofi the threads close to the appearance of the finished work is marred by long dangling thread-ends which must subsequently be cut off with a knife or pair of scissors.

The present invention, therefore, has for an object to provide a simplified and otherwise improved thread-cutting mechanism overcoming the above and other defects of prior mechanisms and capableof long continued and efficient operation without attention onthe part of the operator.

.The invention is preferably embodied in a machine of the well known class- 68 Singer type constructed substantially in accord ance with the disclosures of the patent to C. M.Horton, No. 807,676, clatedDecember 19, 1905, and patent to G. S. Gatchell, No. 798,130, dated August 29, 1905, and, inthe present instance, comprises an unsharpened needle-loop detaining andspreading implement timed to enter and spread the last needle-loop seized by the loop-taker. The throat-plate sustains astationary cutting edge which is formed preferably upon a ledger-blade let into or set flush with the under surface of the throat-plate with its cutting edge closely adjacent the usual nee dlehole. A cutter-blade is sustained to move with the loop-detainer. and spreader and, in the present a beak adapted to work and, consequently, the

instance, is formed with e er th er e e ea.r

loop and guide the limb thereof which leads to the last stitch within the range of action of the shearing blades. The usual bobbinthread pull-off, nipping and severing means are provided to sever the bobbin-thread close to the work and to hold the bobbin-thread end while the firstfew stitchesof a .new group: or series are being formeol. Y f

In the accompanying drawings,, Fig. l is a side elevation of a machine embodying the invention. F ig. 2 is a bottom plan view. Fig. 3 is a bottom plan'view in larger scale of the throat-plate and implements mounted thereon. Fig. 4 isa cross-sectionon the linev 4-4,:Fig. 8. Fig. 5 is a cross-section on the line 5-5,.Fig. 3. Fig. 6 is a detail perspec-l.

tive view of amodification of the invention, and Fig. 7 is a detail perspectiveview ofv the shearing blade shown in Figs. 2 3,4 and 5.

In the preferred. embodiment of the invention, as illustrateduin Figs. 1 to 5, the

machine frame comprises a bed 1 standard- 2, bracket-arm 3and" head 4 sustainingthe reciprocating needle-bar 5 carrying the eye-pointedneedle 6 which cooperates with the usualv oscillating shuttle (not shown) sustained in the raceway beneath'the bed 1 and actuated by means of the. oscillating shuttle-driving the bracket-arm 3 isthe mainshaft 9 car-v ryingoat its forward end the take-up cams cylinder-l0 having the usual peripheral cam-groove 11 which is entered by the. follower roll {12 carried by the usuaLtake-up shaft 8. Journaled within lever 13. The front face .of the cam-cylinder 10 carries a crank-pin 10 which is connected to theneedle-bar 5 by meansv of the usual pitman 14. 1 I

The-main-shaft 9 carries at its rearward end the tight. andloose pulleys 15and 16, respectively, to the former of which is se-. cured the usual stopping camv1 7 with which the upper ,end"l8 ,offtlie stop-motion lever 19 cooperates in a wellf known manner to, stop the machine.- lines in Fig. 1, the main-shaft 9 is provided with a-worm 20;meshing with .the wormwheel 21 secured upon the transverse shaft 22. uponrwhichis fixed the controller-cam wheel 23. This cam-wheel is formed with the usual clamp jogghig cam-grooves one As represented in dotted of which is shown at 2 1 and-is also, provided wit-hfthe usualthreadwntter controlling cam;

. nipper sprin o In the present instance, the invention is shown as embodied in thread-cu'ttinpll'lLC'llzlnism of the type constructed and operated substanhially in accordance with gtllfi) (lisclosures in the aforesaid Horton and Qa'tchell patents. and accordingly, the 1 mechanism has the iisual bobbin or pulls-oil severing implement or blade 26 formed with the inwardly disposed p-ull-o'fl'edee -27 and with the outwardly disposed up-turned lip 27 which enters the circular groove 28 in the .under side of the throat-plate and is formed with a sharpened edge adapted to cutthe bobbin-thread.

In the present needle-thread severing mechanism 'uSe is made of a needle-loop detainingand spreading implement or blade 30 which is preferably shaped substantially the same as the needle-thread cutting blade disclosed in said Horton patent but differs from said last mentioned blade in that it is not provided with an outer sharpened edge-portion for severing the needle-thread. In' the present embodiment of the inventio the outer edge 31 of the blade 30 is blunt throughout its extent and said blade serves merely to detain and spread the last needle-loop.

The blades 26 and 30 are fixedly secured as usual to the radial arm 32 projecting from the hub of the sector-gear 3.3 journaled upon the pin sustained at the under side of the tliioateplate p. Secured'to the arm is the usual thregidmipper 35 having the hooked extremity 36 adapted to wipe across the needle-hole a and nip the beginning end of i the needle-thread drawn down by the shuttle at thebeginning of a sewing operation. The arm also has secured thereto,

m the present instance, the somewhat resilient shank 37 of a cutting blade 38 which bears yieldingly against the under side of the throat-plate and is formed with a cutting edge 39 adapted to cooperate with the edge 40 of the ledger-blade 41 which is set flush with the under surface of the throatplate.

The cutter-blade 38 is preferably formed with a beak 4:2 adapted to enter the spread needle-loop on the detainer blade 30 and positively guide the limb of the needlecp hieh eads o he las s i a W thin he ange of ac ien f t e sh a tters 38 and s Th h ea p 1 upport t e usual pivoted nipperdever e3 carrying the ked x remity ich Hil the b in thread as shown i ,F ig. 5 for the action of the bobbin-thread cutter 29. The lever 43 is formed with a Cam-Slot- 45 which is en? tiered by pin 46 carried by the arm 47 prejeetiag from he hub o he sec or gea e ntler. oi the sinner e i d s losed i antih accura y in the aferesai l' Gatchell patent,

43" having the bifurcated or In the modification oi the invention shown i Fig. 6 the needle-loop detaining and spreading blade 30 and the needle-thread cutting blade 38. are formed of the same piece of metal the blade 38 being joined to the blade 30 by the return bend 48 which is made sufiiciiently light to give the neccssary resiliency to the blade 38 so that the latter will bear yieldingly against the under side of the throat-plate. The bending of the blade 38 upwardly also bringsit nearer to the under surface of the throatplate providing for cutting the thread shorter. ll hether this blade should however, be bent upwardly from the spreader depends upon how short it is desired to cut the thread and also depends on the distance the spreader '30 is spaced away from disclosed in said Horton patent and comprising a rack 49 carried by a slide-bar 50 suitably supported beneath the bed-plate 1 and. having at its rear end a block 51 formed with a notch entered by the reduced lower end of the lever 53 which is pivotally mounted by means of the stud screw 54 on the bracket 55 (represented in dotted lines in Fig. 1).

The lever 53 is provided at its upper end with a follower stud 56 entering the cam-groove 25 of the controlling'camwheel The block 51 carries at its rear end a pin 57 engaged by the forked arm 58 of a bellcrank-lever mounted on the fulcrum stud Y59 and having a rearwardly extending arm 6.0 provided with an endwise yielding pin 61 normally pressed outwardly by means of the spring 62. The stop lever 19 has an extension 19 below its fulcrum point formed with an aperture (513 which is adapted to be entered by the yielding pin 61 when the stop-lever is i upper extremity 13 is -i-'. with the stopping cam 17.

The thread cutter cam groove is so formed that, in the drawing up of the needle-thread loop for the stitch nextpreceding the last timed stitch. the sector gear receives the first stage of its operative movement which advances the point of the lower or bobbin thread cutting blade 26 beyond the needle hole of the shuttle race cover plate so to dra aside and p l e b bb n thread and i su the pr pe lea-cl o th sam With ut int r rence with operative relation ducing through the bellcrank lever 58, 60

the final jog of the slide-bar 50 to produce the final thread-cuttiim' action of the cutterblades 27 and 38. At the start of a new sewing operation the sector gear 33 receives a slight retrograde movement after the first descent of the needle to retract the hooked nipper blade 35 into clamping e a with the free end of the needle-tin drawn down to the loop taker to hold said end during the production of a few fastening stitches, after which the cutter-blades and nroper are wholly retracted into inoperative relation preparatory to a succeeding thread cutting movement.

/Vhile I have shown and described the invention as embodied in a certain well known type of thread-cutting mechanism it is to be understood that the invention is susceptible of embodiment in various other types of thread-cutting mechanism and is other wise susceptible of material modification both in the form and arrangement of the various parts withinthe scope of the invention. Having thus set forth the nature of the invention, what .I claim herein is 1. In a sewing machine, the combination with a reciprocating needle, a loop-taker and a throat-plate having a needle-hole and supporting a thread-cutting edge closely adjacent said needle-hole,.of a needle-loop detaining implement and a shear-cutter including a cutting blade in fixed relation to said needle-loop detaining implement and adapted to coact with said thread-cutting edge to shear off one limb of the detained needle-loop at a point substantially flush with the under surface of the throat-plate and means for moving said implement and cutting blade to detain the needle-loop and shear off one limb thereof.

2 In a sewing machine, the combination with a reciprocating needle, a loop-taker. and a throat-plate having a needle-hole, of a needle-loop detaining implement, and a shear cutter including shearing elements having cooperating cutting edges, one of said elements being so constructed and ar ranged that its cutting edge is located substantially flush wlth the under surface of the throat-plate and closely adjacent the me and die-hole and the othei'fof said elements be- 1ng 1n fixed relation to said needle-loop detainlngfimplement and means for moving the implement to detain the lastneedleloop formed at the end of a stitching operation and the second shear-element to shear off one limb of the detained needle-loop;

In a sewing machine, the combination' with'a'reciprocating needle, a looptaker'and a throat-plate, of a needle-loop detainer and spreader spaced below the un dersurface'of said throat-plate, and. a shear cutter including a resiliently mountedcutter-bla'de in; fixed relation to saidneedle-' loop de'tainer' and spreader and having a cutting edge adapted to bear yieldingly against the under plate and cut the needle-thread.

4. In a sewing machine, the combination v with a reciprocating needle, a loop-taker and" a throat-plate, of a needle-loop detainer and spreader surface of the throat-" spaced below the under surface of said throat-plate, and a shear.

I cutter including a ledger-blade and a cutter blade in fixed relation tov said needle-loop adapted toenter the spread needle-loop and a cutting edge adapted to coact with the ledger-blade to cut one limb only of theneedle-loop.

5. Thread-cutting mechanism for sewing machines comprising a movable needle-loop detainer and and a ledger-blade with which-said cutterbladeis adapted-to cooperate to shear on limb of the detained needle-loop.

spreader, a cutter-bladev resiliently mounted in fixed relation thereto,

6. Thread-cutting mechanism for sewing machines comprising a movable needle-loop I detainer and spreader, a cutter-blade mounted in fixed relation-thereto, and having being also cutting edge, said cutter-blade formedwith a beak adapted to enter the detained needle-loop and guide one limb there'- of to said cutting edge, and a ledger-blade adapted-to with which said cutter-blade is cooperate to shear one limb only tained needle-loop.

of the de- 7. A thread-cutting mechanism for sewing machines comprising a throat-plate having a cutting edge on its under surface, a forwardly and rearwardly movable needle-loop detainer and spreader, and a forwardlydirected cutter-blade movable simultaneously aid spreader and coacting with said 90 l detainer and, spreader and having a beak Cir maol'iines Lomprising a ledger-blade means movable toward and parallel to for detaining and spreading a needle-loop,

and a entterblade movable simultaneously with said means and in the same direction to ooaet with said ledger-blade to shear one limb of the detained loop.

10. In a sewing machine'having stitchforming mechanism including a needle and loop-taker, a throat-plate having a needlehole and supporting; a ledger-blade-edge adjacent the needle-hole, a pointed movable implement adapted to enter and spread a needle-loop, a shear-blade in fixed relation to and movable with I said implement and adapted to c-oaet with said ledger-bladeedge and means for moving the implement said blade to enter and spread the last needle-loop formed in a stitching operation and the shear-blade to shear-cut one limb thereof.

11. In a sewing machine the combination with a needle, a loop-taker and a throat,- plate, of a movable needle-loop detainer and spreader spaced below the under surface of the throat-plate, a shearing cutter located between the detainer and to shear-cut one limb of the needle-loop and including a cutter-blade movable With said needle-loop-detainer and spreader, and means for moving said detainer and spreader and said cutter-blade,

In testimony whereof, I have signed my name to this specification.

ALBERT F. FIFIELD. a

the Work adapted i 

